Like a CV, there is a certain amount of personal preference involved when writing your cover letter. Typically, most will follow similar guidelines, but candidates will no doubt choose different layouts in which to order their information according to preference and the job they are applying for.
Cover all the essential points clearly - remember employers are busy and might not have the time to read a long letter. Use the same language that the employer uses on their website, in job adverts and any other communications. Use the same tone as the employer, but remember to keep it professional. Present your skills in a way that shows how.